What is wetting bricks?
Wetting bricks (pre-wetting) is the practice of dampening bricks before laying them, or applying a thin layer of mortar as a primer, to improve the bond between the brick and the mortar. It prevents dry bricks from sucking the moisture out of the mortar, which would weaken the bond.
Why wet bricks?
Bricks are porous and absorb water. If you apply mortar to a bone-dry brick, the brick draws the water out of the mortar. This causes two problems:
- Poor bond — the mortar dries too quickly and doesn’t adhere properly to the brick
- Weak joints — the mortar doesn’t get the chance to cure fully
By wetting the bricks — briefly dampening or applying a thin mortar slurry — enough moisture stays in the mortar for a good bond and proper curing.
Application
Wetting bricks is relevant when:
- Laying bricks in hot weather — in summer, bricks dry out particularly fast
- Using highly absorbent bricks — some brick types (such as handmade bricks) absorb more water than others
- Repair work — when patching existing brickwork where the bricks have already dried out
- Rendering and plastering — when applying render to a wall, the substrate is sometimes dampened first
Method
In practice, wetting is done in two ways:
- Dampening — briefly dipping the bricks in water or spraying with a hose. Not too wet: the brick should be damp, not dripping.
- Slurry coat — applying a diluted mortar layer to the brick (a kind of primer), before the main mortar is applied.
Related terms
- Bond pattern
- Mortar mix
- Joint
- Bricklaying
- Rendering
Learn more about building terms in our knowledge base at fredsdiyplans.com.